Scientists from 20 countries gather to discuss earthquake geology

28/11/2017 10:47 am

Science update, 28 November 2017 - Around the first anniversary of the 2016 M7.8 Kaikōura earthquake, GNS Science hosted 130 geologists from around the world at a meeting focused on the latest research and advances in earthquake geology. Earthquake geology is a discipline that uses the geological record and landscape features to understand the size and frequency of past large earthquakes.

Field trip participants on the Leader fault in north Canterbury. Here a New Zealand-based postgraduate student discusses her research project on the Leader fault with other students from New Zealand and Japan.

This information is crucial for understanding earthquake hazards and for forecasting the likely location, size and impacts of earthquakes. The meeting, called PATA Days (Paleoseismology, Active Tectonics, Archaeoseismology), has been held annually for the past eight years and this is the first time it has been in the Southern Hemisphere.

The 2017 PATA Days was held in Blenheim and the visiting scientists were taken on a field trip to several of the faults that ruptured in the Kaikōura earthquake. The meeting offered an opportunity for scientists to share the latest research on the Kaikōura earthquake, an unusual earthquake that continues to spur research efforts to understand its complexity. Research from around the world was also presented and discussed, with particularly strong presence at the meeting by scientists from Italy, USA, Spain, Japan, Chile and Greece, along with 15 other countries.

On the 14 November, a public talk was held in Blenheim at which five scientists presented research on earthquake hazards in New Zealand, California and Italy. About 400 people attended and the level of public interest in earthquake research was impressive to many of our international guests. About half the conference participants went on a post-conference field trip around the top of the South Island, visiting several sites along the Wairau fault, Alpine Fault and the Leader Fault in north Canterbury.

The meeting was made possible with support from EQC and project AF8 – an initiative to better prepare for the next large Alpine Fault earthquake.

The 2016 surface rupture of the Kekerengu fault. At this location field trip participants observed the fresh rupture of the Kekerengu fault, a variety of topographic expressions of the fault, and some fencelines crossing the fault that still preserve >8 m horizontal displacements.

Field trip participants spread along the uplifted scarp of the Papatea fault as it crosses the Clarence River. At this location, the river bank on the left side of the photo was uplifted about 9 m relative to the other side of the river. Rapid incision by streams and the river through this newly uplifted riverbank is creating rapids and impressive erosional features.

Field trip participants walking across the scarp of the Papatea fault. The slope in the grass paddock and the tilted pine trees were created by the 2016 surface rupture of the Papatea fault. One side of the paddock rose ~7 m higher than the other and throughout the paddock fissures and ruptures in the ground surface can still be seen.

Geologists examining the complex tectonic environment at the toe of the Leader landslide. Here the stream was diverted by the landslide and has cut down through a river terrace creating a new geological exposure of a fault line. The 2016 fault rupture crosses the stream and offsets different rock layers. This type of outcrop can yield information about past earthquakes.

Fieldtrip participants at Marble Hill, near Springs Junction, where a concrete wall was constructed in 1964 across the Alpine fault to monitor the fault for slow, creeping movement. Geologists are discussing the lack of creep and the earthquake history of the Alpine fault. Here the fault has moved river terraces of different ages – older river terraces are displaced by a greater amount across the fault than younger terraces. This information tells us about the slip rate of the fault and the timing and size of past earthquakes.